Mono-azo dyes and inks for ink-jet printing

ABSTRACT

A mono-azo compound of Formula (1) or a salt thereof:wherein:A is N, C-Cl, C-CN or C-NO2;R1 is H or optionally substituted alkyl;G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, -CF3, halo or -PO3H2;L1 and L2 each independently is -SR2, -OR3 or -NR4R5;R2, R3, R4 and R5 each independently is H, optionally substituted alkyl or optionally substituted aryl; orR4 and R5 together with the nitrogen to which they are attached form an optionally substituted five or six membered ring;provided that L1 and L2 are free from carboxy, sulpho and -PO3H2 groups; and the use of a mono-azo compound of Formula (1) or a salt thereof in inks, an ink jet printing process using the inks, a substrate printed with the inks and an ink jet printer cartridge containing the inks.

This invention relates to dyes, to inks and to their use in ink jet printing (“IJP”). IJP is a non-impact printing technique in which droplets of ink are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.

There are many demanding performance requirements for dyes and inks used in IJP. For example they desirably provide sharp, non-feathered images having good water-fastness, light-fastness and optical density. The inks are often required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink jet nozzle because this will stop the printer from working. The inks should also be stable to storage over time without decomposing or forming a precipitate which could block the fine nozzle.

According to the present invention there is provided a mono-azo compound of Formula (1) or a salt thereof:

wherein:

A is N, C—Cl, C—CN or C—NO₂;

R¹ is H or optionally substituted alkyl;

G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, —CF₃, halo or —PO₃H₂;

L¹ and L² each independently is —SR², —OR³ or —NR⁴R⁵;

R², R³, R⁴ and R⁵ each independently is H, optionally substituted alkyl or optionally substituted aryl; or

R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted five or six membered ring;

provided that L¹ and L² are free from carboxy, sulpho and —PO₃H₂ groups.

The term mono-azo refers to compounds of Formula (1) with one azo group (—N═N—).

Preferably A is N.

R¹ is preferably H or optionally substituted C₁₋₄-alkyl, more preferably H or C₁₋₄-alkyl optionally substituted by hydroxy, carboxy, sulpho or cyano. Examples include methyl, ethyl, n-propyl, iso-propyl, hydroxyethyl, cyanoethyl, sulphopropyl and carboxyethyl. It is especially preferred that R¹ is H.

G is preferably attached ortho to the azo group. Preferably G is —SO₃H, —COOH, —CF₃, alkyl (preferably optionally substituted C₁₋₄-alkyl), alkoxy (preferably optionally substituted C₁₋₄-alkoxy) or —PO₃H₂, more preferably —SO₃H, —COOH or —CF₃ and especially —SO₃H. Preferred optional substituents on G are selected from —OH, —SO₃H, —COOH and —NH₂.

When R², R³, R⁴ or R⁵ is optionally substituted alkyl it is preferably optionally substituted C₁₋₃₀-alkyl, The alkyl group may be straight-chain, branched-chain or cyclic (for example cyclohexyl). When it is a branched-chain alkyl, it is preferably an α-branched alkyl group, for example —CH(CH₃)CH₂CH₂CH₃ or —CH(CH₃)CH₂CH(CH₃)₂. In one preferred embodiment the alkyl group is optionally substituted C₁₋₁₀-alkyl, more preferably optionally substituted C₁₋₆-alkyl and especially optionally substituted C₁₋₄-alkyl. In a further preferred embodiment the alkyl group is optionally substituted C₅₋₂₀-alkyl.

Preferred optional substituents on the alkyl groups represented by any of R², R³, R⁴ or R⁵ include hydroxy, cyano, halo (especially F or Cl), nitro, C₁₋₆-alkoxy, C₁₋₆hydroxyalkoxy, a 5 or 6 membered heterocyclic group, or a group represented by T, wherein T is an optionally substituted amino group. Especially preferred substituents are selected from hydroxy, a 5 or 6 membered heterocyclic group and a group represented by T. Preferred 5 or 6 membered heterocyclic groups are optionally substituted furanyl and tetrahydrofuranyl, more preferably furanyl or tetrahydrofuranyl and especially furan-2-yl and tetrahydrofuran-2-yl.

Preferably T is a group of the formula —NR⁶R⁷ wherein R⁶ and R⁷ are each independently H, optionally substituted alkyl, —CO(alkyl), —CO(phenyl), or R⁶ and R⁷ together with the nitrogen to which they are attached form an optionally substituted morpholinyl, piperazinyl or piperidinyl ring.

When R⁶ or R⁷ is optionally substituted alkyl it is preferably optionally substituted C₁₋₂₀-alkyl, more preferably optionally substituted C₁₋₆alkyl, and especially C₁₋₄-,alkyl, for example methyl, ethyl, n-propyl and iso-propyl. Preferred optional substituents on R⁶ and R⁷ are selected from —OH or —NH₂.

When R⁶ or R⁷ is —CO(alkyl) it is preferably —CO(C₁₋₆-alkyl), more preferably —CO(C₁₋₄-alkyl). For example —COCH₂CH₃ and —COCH₂CH₂CH₃.

When R⁶ and R⁷ together with the nitrogen to which they are attached form a substituted morpholinyl, piperidinyl or piperazinyl ring it is preferably substituted by C₁₋₄-alkyl, C₁₋₄-hydroxyalkyl, —CO(C₁₋₄-alkyl) or a group of the formula —M—NR⁸R⁹ wherein M is an alkylene linking group and R⁸ and R⁹ each independently is H or C₁₋₆-alkyl optionally substituted by hydroxy or C₁₋₆-alkoxy. M is preferably C₁₋₆-alkylene, more preferably C₂₋₆-alkylene and especially —(CH2)_(g)—, wherein g is from 2 to 6.

Further preferred groups represented by T include —NH₂; —NH(C₁₋₃₀(-alkyl), for example ethylamino, —NHCH(CH)₃CH₂CH₃ and —NHC₁₆H₃₃; —N(C₁₋₆-alkyl)₂, for example di-ethylamino; —NHCO(C₁₋₄-alkyl), for example —NHCOCH₃ and —NHCOCH₂CH₃; —NH(Phenyl); morpholinyl; piperazinyl; and substituted piperazinyl groups of the Formula (2):

wherein:

Y is C₁₋₄-alkyl, C₁₋₄-hydroxyalkyl, —CO(C₁₋₄-alkyl) or a group of the formula —M—NR⁸R⁹; and

M, R⁸ and R⁹ are as hereinbefore defined.

Preferred groups of the Formula (2) include for example:

A preferred alkyl group substituted by T which may be represented by any of R², R³, R⁴ and R⁵ is of the formula —(C_(d)H_(2d))—T wherein d is 1 to 6, more preferably 2 to 6 and T is as hereinbefore defined.

A further preferred optionally substituted alkyl group represented by any of R², R³, R⁴ and R⁵ is of the Formula (3):

—(C_(a)H_(2a)O)_(t)(C_(b)H_(2b)O)_(q)R¹⁰  Formula (3)

wherein:

R¹⁰ is H or alkyl optionally substituted by —NH₂;

a and b are different and from 1 to 6;

t is from 1 to 4; and

q is from 0 to 3.

Preferably R¹⁰ is H or C₁₋₄-alkyl, more preferably H.

Preferably a and b are each independently 2 to 6, more preferably 2 or 3, t is 1 or 2 and q is 0.

Preferred groups of Formula (3) include —(C₂₋₆-alkylene)O(C₂₋₆-alkylene)OC₁₋₄alkyl, for example —C₂H₄OC₂H₄OCH₃, and —(C₂₋₆-alkylene)O(C₂₋₆-alkylene)OH, for example —C₂H₄OC₂H₄OH, —CH₂CH(CH₃)CH₂OC₂H₄OH and —C₃H₆OC₂H₄OH.

When R², R³, R⁴ or R⁵ is optionally substituted aryl it is preferably optionally substituted phenyl or optionally substituted naphthyl, more preferably a group of the Formula (4) or (5):

wherein:

each R¹¹ independently is C₁₋₆-alkoxy, C₁₋₆-hydroxyalkoxy, hydroxy, halo (preferably F or Cl), nitro, amino, —COC₁₋₆-alkyl, —NHCOC₁₋₆-alkyl or —NHC₁₋₆-hydroxyalkyl;

each Q independently is optionally substituted C₁₋₃₀-alkyl or a group of the Formula —Z—Q¹;

each Z independently is a divalent linking group;

each Q¹ independently is optionally substituted C₁₋₃₀-alkyl;

n and m each independently is 0 to 5; and

(n+m)=0 to 5.

m is preferably 0, 1 or 2, more preferably 1 or 2.

n is preferably 0 or 1.

(n+m) is preferably 1 to 3 more preferably 1 or 2.

Each Z is preferably independently selected from —O—, —S—, —NR^(a)—, —SO₂— and —SO₂NR^(a)—, wherein R^(a) is H or C₃₀-alkyl optionally substituted by a group other than —COOH, —SO₃H or —PO₃H₂. Preferably R^(a) is H or C₁₋₂₀-alkyl, more preferably H or C₁₋₆-alkyl and especially H.

Q and Q¹ may be a straight chain or branched chain alkyl group. When any of Q or Q¹ is a branched chain alkyl group it is preferably branched at the α-carbon. In a preferred embodiment Q and Q¹ are each independently C₁₋₄-alkyl. In a further preferred embodiment Q and Q¹ are each independently optionally substituted C₅₋₂₀-alkyl.

When any of Q or Q¹ is substituted, the substituents are preferably selected from hydroxy, cyano, halo (especially F or Cl), nitro, C₁₋₆-alkoxy, C₁₋₆-hydroxyalkoxy, a 5 or 6 membered heterocyclic group, or a group represented by T, wherein T is as hereinbefore defined. It is preferred, however, that Q and Q¹ are unsubstituted.

Preferably R⁴ and R⁵ are not both optionally substituted aryl.

When R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted 5 or 6 membered ring it is preferably a morpholinyl or an optionally substituted piperazinyl ring. The substituents are preferably selected from hydroxy, halo, C₁₋₆-alkoxy, C₁₋₆-alkyl and C₁₋₆-alkyl substituted by hydroxy or a group represented by T as hereinbefore defined. More preferably the substituents are selected from C₁₋₆-alkyl or a group of the formula —C₁₋₆-alkylene-T. When R⁴ and R⁵ together with the nitrogen to which they are attached form a substituted piperazinyl ring it is preferably substituted on a nitrogen atom.

It is especially preferred that when R⁴ and R⁵ together with the nitrogen to which they are attached form a 5 or 6 membered ring it is morpholinyl, piperazinyl or piperidinyl optionally substituted by C₁₋₄-alkyl or C₁₋₄-hydroxyalkyl.

R², R³, R⁴ and R⁵ are preferably free from sulphatoethylsulphonyl and vinylsulphone groups.

It is preferred that R², R³, R⁴ and R⁵ are each independently H, C,₁₋₃₀-alkyl optionally substituted by hydroxy, a 5 or 6 membered heterocyclic group or a group represented by T, or R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted morpholinyl, piperidinyl or piperazinyl ring.

Preferred groups of the formula —NR⁴R⁵ include —NHR⁵, morpholinyl, piperidinyl or piperazinyl optionally substituted by C₁₋₆-alkyl or a group of the formula —(C₁₋₆-alkylene)—T wherein T and R⁵ are as hereinbefore defined.

When L¹ and/or L² is a group of the formula —NHR⁵ it is preferably of the formula—NHR^(b), wherein R^(b) is —(C₁₋₆-alkylene)O(C₁₋₆-alkylene)OR¹⁰; a group of the Formula (4); or C₁₋₃₀-alkyl optionally substituted by one or more of furanyl, tetrahydrofuranyl, —OH or T wherein T, R¹⁰ and Formula (4) are as hereinbefore defined. Preferably R^(b) is C₁₋₃₀-alkyl optionally substituted by one or more of —OH, furanyl, tetrahydrofuranyl or T wherein T is as hereinbefore defined. It is especially preferred that R^(b) is C₁₋₆-alkyl optionally substituted by two to five —OH groups. A further preferred group of the formula —NHR^(b) is of the formula —NH(C_(d)H_(2d))—T wherein d is 1 to 6

Examples of preferred groups of the formula —NHR^(b) which may be represented by L¹ and L² include:

A first preferred embodiment of the present invention comprises a compound of the Formula (6) or a salt thereof:

wherein:

X¹ and X² each independently is —O—, —S—or —NR¹²—;

W¹ and W² each independently is H, a group T, —O(C₁₋₆-alkylene)OR¹⁰, C₁₋₆-alkoxy, hydroxy or a 5 or 6 membered heterocyclic group;

R¹² is H or C₁₋₂₀-alkyl (preferably C₁₋₆-alkyl) optionally substituted by hydroxy, C₁₋₄-alkoxy or a group T;

p and q are each independently 1 to 20; or

—X¹—(C_(p)H_(2p))W¹ and —X²—(C_(q)H_(2q))W² each independently form a piperazinyl, morpholinyl or piperidinyl ring; and

T, R¹ and R¹⁰ are as hereinbefore defined;

provided that W¹, W² and R¹² are free from carboxy, sulpho and —-PO₃H₂ groups.

In one embodiment p and q each independently is 1 to 4 and in a second embodiment p and q each independently is from 5 to 20.

The compounds of Formula (6) provide prints which exhibit a high light-fastness when incorporated into inks for ink jet printing. The compounds of Formula (6) are also highly soluble which improves operability and reduces crusting when inks containing the compounds are used in an ink jet printer.

When W¹ or W² is a 5 or 6 membered heterocyclic group it is preferably piperazinyl, morpholinyl, furanyl or tetrahydrofuranyl, more preferably it is morpholinyl, piperazinyl, furan-2-yl, or tetrahydrofuran-2-yl of the formula:

R¹² is preferably H or C₁₋₄-alkyl optionally substituted by hydroxy. It is especially preferred that R¹² is H.

A second preferred embodiment of the present invention comprises a compound of Formula (6) and salts thereof wherein

X¹ and X² each independently is —NR¹²—(preferably —NH—); and

W¹, W², R¹, R¹², p and q are as hereinbefore defined;

provided that W¹, W² and R¹² are free from carboxy, sulpho and —PO₃H₂ groups.

A third preferred embodiment of the present invention comprises a compound of Formula (6) or a salt thereof wherein:

W¹ and W² each independently is H, —OC₁₋₆-alkylene—OR¹⁰, C₁₋₆-alkoxy, —NH₂, —NR³CO(C₁₋₄-alkyl), hydroxy, morpholinyl or tetrahydrofuranyl;

R¹³ is H or C₁₋₄-alkyl; and

X¹, X², R¹, R¹⁰, R¹², p and q are as hereinbefore defined.

A fourth preferred embodiment of the present invention comprises a compound of the Formula (7) or a salt thereof:

wherein:

R¹, X¹, X², W¹, Q, m and p are as hereinbefore defined;

provided that W¹, X¹, X² and each Q are free from carboxy, sulpho and —PO₃H₂ groups.

Especially preferred compounds of the Formula (7) are those wherein R¹ is H or C₁₋₄-alkyl; X¹ and X² each independently is —S— or —NR¹²— (more preferably —NH—), wherein R¹² is as hereinbefore defined; W¹ is H, tetrahydrofuranyl or —OH; each Q independently is

C₁₋₂₀-alkyl (more preferably C₅₋₂₀-alkyl); m is 0, 1 or 2; and p is 1-20 (more preferably 5 to 20).

Further preferred compounds of Formula (7) are those wherein each Q independently is C₁₋₄-alkyl.

A fifth preferred embodiment of the present invention comprises compounds of the Formula (1) and salts thereof wherein G is —SO₃H and is attached ortho to the azo group; L¹ and L² each independently is —NHR^(b) wherein R^(b) is as hereinbefore defined; and R¹ is H or C₁₋₄-alkyl. In a further embodiment L¹ and/or L² contains an α-branched alkyl group.

The compounds of the invention may be in the free acid or salt form. Preferred salts are water-soluble, for example alkali metal salts, especially lithium, sodium and potassium salts, ammonium and substituted ammonium salts. Especially preferred alkali metal salts are those with sodium and lithium.

Especially preferred ammonium and substituted ammonium salts have cations of the formula *NV₄ wherein each V independently is H or optionally substituted alkyl, or two groups represented by V are H or optionally substituted alkyl and the remaining two groups represented by V, together with the N atom to which they are attached, form a 5- or 6-membered ring (preferably a morpholinyl, pyridinyl or piperidinyl ring).

Preferably each V independently is H or C₁₋₄-alkyl, more preferably H, CH₃ or CH₃CH₂, especially H. Thus the cation is preferably ammonium (i.e.⁺NH₄).

Examples of cations include ⁺NH₄, morpholinium, piperidinium, pyridinium, (CH₃)₃N⁺H, (CH₃)₂N⁺H₂, H₂N⁺(CH₃)(CH₂CH₃),CH₃N⁺H₃, CH₃CH₂N⁺H₃, H₂N⁺(CH₂CH₃)₂, CH₃CH₂CH₂N⁺H₃, CH₃CH₂CH₂N⁺H₃, (CH₃)₂CHN⁺H₃, N⁺(CH₃)₄, N⁺(CH₂CH₃)₄, N-methyl pyridinium, N,N-dimethyl piperidinium and N,N-dimethyl morpholinium.

The compounds may be converted into a salt using known techniques. For example, an alkali metal salt of a dye may be converted into a salt with ammonia or an amine by dissolving an alkali metal salt of the dye in water, acidifying with a mineral acid and adjusting the pH of the solution to pH 9 to 9.5 with ammonia or the amine and removing the alkali metal cations by dialysis.

The present invention covers all tautomeric forms of the compounds shown in this specification, for example the hydrazo tautomers.

The present invention also covers mixtures comprising one or more compounds of the Formula (1); and mixtures comprising one or more compounds of the Formula (1) and one or more water-soluble dye (preferably a magenta dye) other than a compound of Formula (1). For example a mixture comprising a compound of Formula (1) and one or more water-soluble magenta dye selected from a xanthene dye, an azo dye and a bis azo dye.

The compounds of the invention may be prepared using conventional techniques for the preparation of azo dyes. For example a suitable method comprises condensing a compound of the Formula (8) with a compound of the Formula L²H:

wherein A, R¹, G, L¹ and L² are as hereinbefore defined.

The condensation is preferably performed in a liquid medium, more preferably an aqueous medium and especially water. Temperatures of 15° C. to 100° C. are preferred, more preferably from 60 to 70° C. Preferably a reaction time of 1 to 48, more preferably 3 to 24 hours is used.

The condensation is preferably performed in the presence of a base. The base may be any inorganic base for example, ammonia, an alkali metal or alkali earth metal hydroxide, carbonate or bicarbonate, or an organic base. Preferred organic bases are tertiary amines for example, N-alkylated heterocycles, for example N-(C₁₋₄-alkyl)morpholine, N-(C₁₋₄-alkyl)piperidine, N,N′-di(C₁₋₄-alkyl)piperazine; tri(C₁₋₄-alkyl)amines, for example triethylamine, and optionally substituted pyridines, especially pyridine.

The amount of base used may be varied between wide limits but it is preferred to use less than 40, more preferably less than 10 and especially from 3 to 5 moles for each mole of the compound of Formula (8).

After the condensation the product may be isolated by precipitating the product as a salt from the reaction mixture for example by the addition of a suitable alkali metal salt, especially sodium chloride. Alternatively, the product may be isolated in its free acid form by acidifying the reaction mixture, preferably using a mineral acid, especially hydrochloric acid. Where the product precipitates as a solid it may be separated from the mixture by filtration.

If desired unwanted anions may be removed from the product of the above process by dialysis, osmosis, ultrafiltration or a combination thereof.

The product of the above process may be converted, if desired, to the NH₄ ⁺, quaternary ammonium or organic amine salt by the addition of ammonia, ammonium hydroxide, primary, secondary, tertiary or quaternary amine. When the base used in the condensation process is an organic amine an excess may be used so that the compound of Formula (1) is formed as the organic amine salt.

The compound of the Formula (8) may be prepared using conventional techniques, for example by:

(1) diazotising the compound of the formula:

wherein G is as hereinbefore defined, to give the corresponding diazonium salt;

(2) coupling the diazonium salt from stage (1) with 2-amino-8-naphthol-3,6-disulphonic acid at a pH<7, preferably at a pH of from 3 to 5;

(3) alkaline hydrolysis of the product of stage (2) to remove the acetyl group;

(4) condensing the product from stage (1) with a compound of the formula:

wherein A is as hereinbefore defined; and

(5) condensing the product from stage (4) with approximately 1 molar equivalent of the compound of the formula L¹H.

The diazotisation in stage (1) is preferably performed in an aqueous medium at a pH below 7 in the presence of a suitable diazotisation agent. Dilute mineral acid, e.g. HCl or H₂SO₄, is preferably used to achieve the desired acidic conditions. Conveniently the diazotisation agent is formed in-situ, for example by dissolving an alkali metal nitrite, preferably sodium nitrite, in a molar excess of mineral acid, preferably HCl. Normally at least one mole of diazotisation agent per mole of the amine in stage (1) preferably from 1 to 1.25 moles will be used in the diazotisation.

The temperature of the diazotisation is not critical and may conveniently be carried out at from −5° C. to 20° C., preferably from 0 to 10° C. and especially from 0 to 5° C.

The hydrolysis in stage (3) is preferably performed at a pH in the range 9 to 14.

The temperature during hydrolysis is preferably from 40 to 90° C.

The compounds of Formula (1) are useful as dyes, especially for the coloration of inks for ink jet printing.

According to a second aspect of the present invention there is provided an ink comprising:

(a) from 0.01 to 30 parts of a compound of the Formula (9); and

(b) from 70 to 99.99 parts of a medium comprising (i), (ii) or (iii):

(i) a mixture of water and an organic solvent;

(ii) an organic solvent free from water; or

(iii) a low melting point solid;

wherein all parts are by weight and the number of parts of (a)+(b)=100:

wherein:

L³ is L¹ or a labile atom or group;

L⁴ is L² or a labile atom or group;

A, R¹, G, L¹ and L² are as hereinbefore defined;

provided that L³ and L⁴ are free from carboxy, sulpho and —PO₃H₂ groups.

When L³ or L⁴ is a labile atom or group, it is preferably an atom or group which is bound by a chemical bond to the compound of Formula (9) which is displaceable by a hydroxyl group of cellulose under mildly alkaline aqueous conditions to form a covalent bond between the compound of Formula (9) and cellulose.

Preferred labile atoms and groups represented by L³ and L⁴ include halogen atoms, for example F and Cl; thiocyano groups; quaternary ammonium groups, for example trialkylammonium groups and optionally substituted pyridinium groups.

Preferably L³ is L¹ and L⁴ is L² as hereinbefore defined for the first aspect of the invention.

In the inks according to the second aspect of the present invention the compound of Formula (9) is preferably of Formula (1), more preferably of Formula (6) or (7) as hereinbefore defined.

The number of parts of component (a) is preferably from 0.1 to 20, more preferably from 0.5 to 15, and especially from 1 to 5 parts. The number of parts of component (b) is preferably from 99.9 to 80, more preferably from 99.5 to 85, especially from 99 to 95 parts.

When the medium is a mixture of water and an organic solvent or an organic solvent free from water, preferably component (a) is completely dissolved in component (b). Preferably component (a) has a solubility in component (b) at 20° C. of at least 10%. This allows the preparation of concentrates which may be used to prepare more dilute inks and reduces the chance of the dye precipitating if evaporation of the liquid medium occurs during storage.

When the medium comprises a mixture of water and an organic solvent, the weight ratio of water to organic solvent is preferably from 99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from 95:5 to 80:20.

It is preferred that the organic solvent present in the mixture of water and organic solvent is a water-miscible organic solvent or a mixture of such solvents. Preferred water-miscible organic solvents include C₁₋₆-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol and cyclohexanol; linear amides, preferably dimethylformamide or dimethylacetamide; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscible ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol; mono-C₁₋₄-alkyl ethers of diols, preferably mono-C₁₋₄-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclic esters, preferably caprolactone; sulphoxides, preferably dimethyl sulphoxide and sulpholane. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-soluble organic solvents.

Especially preferred water-soluble organic solvents are cyclic amides, especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone; diols, especially 1,5-pentane diol, ethyleneglycol, thiodiglycol, diethyleneglycol and triethyleneglycol; and mono-C₁₋₄-alkyl and C₁₋₄-alkyl ethers of diols, more preferably mono-C₁₋₄-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxy-2-ethoxy-2-ethoxyethanol.

A preferred medium comprises:

(a) from 75 to 95 parts water; and

(b) from 25 to 5 parts in total of one or more solvents selected from diethylene glycol, 2-pyrrolidone, thiodiglycol, N-methylpyrrolidone, cyclohexanol, caprolactone, caprolactam and pentane-1,5-diol;

wherein the parts are by weight and the sum of the parts (a) and (b)=100.

Examples of further suitable ink media comprising a mixture of water and one or more organic solvents are described in U.S. Pat. Nos. 4,963,189, 4,703,113, 4,626,284 and EP 4,251,50A.

When the liquid medium comprises an organic solvent free from water, (i.e. less than 1% water by weight) the solvent preferably has a boiling point of from 30° to 200° C., more preferably of from 40° to 150° C., especially from 50 to 125° C. The organic solvent may be water-immiscible, water-miscible or a mixture of such solvents. Preferred water-miscible organic solvents are any of the hereinbefore described water-miscible organic solvents and mixtures thereof. Preferred water-immiscible solvents include, for example, aliphatic hydrocarbons; esters, preferably ethyl acetate; chlorinated hydrocarbons, preferably CH₂Cl₂; and ethers, preferably diethyl ether; and mixtures thereof.

When the liquid medium comprises a water-immiscible organic solvent, preferably a polar solvent is included because this enhances solubility of the dye in the liquid medium. Examples of polar solvents include C₁₋₄-alcohols. In view of the foregoing preferences it is especially preferred that where the liquid medium is an organic solvent free from water it comprises a ketone (especially methyl ethyl ketone) &/or an alcohol (especially a C₁₋₄-alkanol, more especially ethanol or propanol).

The organic solvent free from water may be a single organic solvent or a mixture of two or more organic solvents. It is preferred that when the medium is an organic solvent free from water it is a mixture of 2 to 5 different organic solvents. This allows a medium to be selected which gives good control over the drying characteristics and storage stability of the ink.

Ink media comprising an organic solvent free from water are particularly useful where fast drying times are required and particularly when printing onto hydrophobic and non-absorbent substrates, for example plastics, metal and glass.

Preferred low melting solid media have a melting point in the range from 60° C. to 125° C. Suitable low melting point solids include long chain fatty acids or alcohols, preferably those with C₁₈₋₂₄ chains, and sulphonamides. The dye of Formula (9) may be dissolved in the low melting point solid or may be finely dispersed in it.

The compounds according to the present invention exhibit a high solubility in aqueous media, accordingly it is preferred that the liquid medium is a mixture of water and one or more water miscible organic solvent(s).

The ink may also contain additional components conventionally used in ink jet printing inks, for example viscosity and surface tension modifiers, corrosion inhibitors, biocides, kogation reducing additives and surfactants which may be ionic or non-ionic.

The presence of impurities in an ink jet printing ink can result in the formation of precipitates in the ink. This is undesirable because the precipitates can block the narrow ink jet nozzle in the printer. Therefore, the compounds(s) according to the first aspect of the present invention may be, and preferably are, purified to remove undesirable impurities before they are incorporated into inks for ink jet printing. Conventional techniques may be employed for purifying the compounds, for example osmosis and/or dialysis.

A third aspect of the present invention provides a process for printing an image on a substrate comprising applying thereto an ink containing a compound of Formula (9) as hereinbefore defined by means of an ink jet printer.

The Preferred ink used in this process is an ink according to the second aspect of the present invention.

The ink jet printer preferably applies the ink to the substrate in the form of droplets which are ejected through a small orifice onto the substrate. Preferred ink jet printers are piezoelectric ink jet printers and thermal ink jet printers. In thermal ink jet printers, programmed pulses of heat are applied to the ink in a reservoir by means of a resistor adjacent to the orifice, thereby causing the ink to be ejected in the form of small droplets directed towards the substrate during relative movement between the substrate and the orifice. In piezoelectric ink jet printers the oscillation of a small crystal causes ejection of the ink from the orifice.

The substrate is preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper.

Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character. Examples of commercially available papers include, HP Premium Coated Paper, HP Photopaper (all available from Hewlett Packard Inc), Stylus Pro 720 dpi Coated Paper, Epson Photo Quality Glossy Film, Epson Photo Quality Glossy Paper (available from Seiko Epson Corp.), Canon HR 101 High Resolution Paper, Canon GP 201 Glossy Paper, Canon HG 101 High Gloss Film (all available from Canon Inc.), Wiggins Conqueror paper (available from Wiggins Teape Ltd), Xerox Acid Paper and Xerox Alkaline paper.

A fourth aspect of the present invention provides a paper, an overhead projector slide or a textile material printed with an ink according to the second aspect of the present invention, or by means of the process according to the third aspect of the present invention.

When the substrate is a textile material the ink according to the invention is preferably applied thereto by:

i) applying the composition to the textile material using an ink jet printer; and

ii) heating the printed textile material at a temperature of from 50° C. to 250° C.

Preferred textile materials are natural, synthetic and semi-synthetic materials. Examples of preferred natural textile materials include wool, silk, hair and cellulosic materials, particularly cotton, jute, hemp, flax and linen. Examples of preferred synthetic and semi-synthetic materials include polyamides, polyesters, polyacrylonitriles and polyurethanes.

Preferably the textile material has been treated with an aqueous pretreatment composition comprising a thickening agent and optionally a water-soluble base and a hydrotropic agent and dried prior to step i) above.

The pre-treatment composition preferably comprises a solution of the base and the hydrotropic agent in water containing the thickening agent. Particularly preferred pre-treatment compositions are described more fully in EP-A-534 660.

A fifth aspect of the present invention provides an ink jet cartridge containing an ink, wherein the ink contains a compound of the Formula (9) as hereinbefore defined in relation to the second aspect of the present invention.

Preferably the ink jet cartridge contains an ink according to the second aspect of the invention.

The invention is further illustrated by the following Examples in which all parts and percentages are by weight unless otherwise stated.

EXAMPLE 1

Dye

Dye (1) was prepared using the process described below:

Stage (i): Diazotisation and Coupling

To N-acetyl p-phenylenediamine sulphonic acid (0.5 moles) in water (400 ml) was added concentrated hydrochloric acid (250 ml) and the solution was cooled to 0-5° C. 2N sodium nitrite (250 ml) was added dropwise over 5 minutes with stirring. After 15 minutes, excess nitrous acid was destroyed by the addition of sulphamic acid (0.2 g). To the resulting suspension was added a solution of 2-amino-8-naphthol-3,6-disulphonic acid (0.5 moles in 600 ml of water at pH6) and the pH was adjusted to 4 by the addition of sodium acetate. The mixture was stirred at 0-5° C. for 4 hours before being allowed to warm to room temperature.

Stage (ii) Hydrolysis

The acetyl group present on the product of stage (i) was removed by alkaline hydrolysis by adding concentrated sodium hydroxide (200 ml) to the mixture resulting from stage 1 and heating at 70-80° C. for 1.5 hours.

After cooling to room temperature, the pH was adjusted to 7 by the addition of concentrated hydrochloric acid. Sodium chloride (20% weight/volume) was added and the precipitated solid was collected by suction filtration, washed with 30% brine and dried at 70° C. Yield 132 g (strength 45%).

Stage (iii) Condensation With Cyanuric Chloride

The product from stage (ii) (0.15 moles) was dissolved in water (500 ml) at pH7. Cyanuric chloride (0.17 moles) was dissolved in acetone (300 ml) and added dropwise over 10 minutes to the stirred solution at 0-5° C. The mixture was stirred for 40 minutes at this temperature.

Stage (iv) Condensations

2-aminoethyoxyethanol (0.5 mole) dissolved in water (400 ml) was added to the mixture from stage (iii). The pH of the reaction mixture was raised to 7 with 2N sodium hydroxide solution and this was maintained whilst the mixture was heated initially to 30-40° C. for 2 hours and finally to 40-50° C. and at a pH of 8.5-9 for 16 hours.

The mixture was cooled to room temperature and evaporated to dryness. The solid was slurried in methylated spirits, collected by suction filtration and washed with further methylated spirits.

Stage (v) Purification

The product of stage (iv) was redissolved in distilled water and dialysed using Visking tubing to a permeate conductivity of below 100 μS. Yield 31.5 g.

Ink

Ink 1 was prepared by dissolving 2 parts of Dye (1) in 98 parts of a mixture comprising 90 parts water and 10 parts 2-pyrrolidone.

Ink Jet Printing

Ink 1 was loaded into an HP Deskjet 560c ink jet printer and was printed onto HP Premium Glossy Paper (available from Hewlett Packard Inc.). The resulting print was a bright magenta which had a good optical density and excellent light fastness.

The optical density of the print was 2.28, as measured using an X-Rite densitometer.

The print exhibited a ΔE value of 1 and an optical density loss of just 4% after 64 hours irradiation in the Atlas Weatherometer.

EXAMPLES 2 TO 4

Dyes of the general Formula (A)

The Dyes of Formula (A) were prepared by condensing the product of stage (iii) in Example 1 with the compound of the formula L¹H, followed by a further condensation with the compound L²H, wherein L¹H and L²H are shown in Table 1.

Each dye in Table 1 was formulated into an ink comprising 2 parts of the dye and 98 parts of a mixture comprising 90 parts water and 10 parts 2-pyrrolidone as described in Example 1. Each ink was then applied to HP Premium Glossy Paper using the same ink jet printer used in Example 1. The resulting prints had the ΔE and reflected optical density values shown in the final two columns of Table 1.

TABLE 1 Exam- ple L¹H L²H ΔE ROD 2 H₂N(C₂H₄)O(C₂H₄)OH 1-(3-aminopropyl)- 2.8 1.70 morpholine 3 Furfurylamine Furfurylamine 3.3 1.89 4 Tetrahydrofurfurylamine Tetrahydrofurfurylamine 3.7 1.59

EXAMPLES 5 TO 18

Further dyes of the general Formula (A) were prepared by condensing the product of stage (iii) in Example 1 with the compound of the formula L¹H, followed by a further condensation with the compound L²H, wherein L¹H and L²H are shown in Table 2.

The dyes provided bright magenta prints with a good optical density, water-fastness and high light-fastness when incorporated into inks which were applied to a paper substrate using an ink jet printer as described above in Examples 1 and 2.

TABLE 2 Example L¹H L²H  5

 6

 7

 8

 9

10

11 H₂NC₁₆H₃₃

12

13 HSC₁₀H₂₁

14 H₂N(CH₂)₆OH

15

16 H₂NC₁₆H₃₃

17 H₂NC₂H₄OC₂H₄OH

EXAMPLE 18

The inks described in Tables 3 and 4 may be prepared wherein the Dye described in the first column is the Dye made in the above Example of the same number. Numbers quoted in the second column onwards refer to the number of parts of the relevant ingredient and all parts are by weight. The inks may be applied to paper by thermal or piezo ink jet printing.

The following abbreviations are used in Table 3 and 4:

PG=propylene glycol

DEG=diethylene glycol

NMP=N-methyl pyrrolidone

DMK=dimethylketone

IPA=isopropanol

MEOH=methanol

2P=2-pyrrolidone

MIBK=methylisobutyl ketone

P12=propane-1,2-diol

BDL=butane-2,3-diol

CET=cetyl ammonium bromide

PHO=Na₂HPO₄ and

TBT=tertiary butanol

TDG=thiodiglycol

TABLE 3 Dye Na Dye Content Water PG DEG NMP DMK NaOH Stearate IPA MEOH 2P MIBK  2  2.0 80 5 6 4  5  4  3.0 90 5 5 0.2  7 10.0 85 3 3 3 5  1  5  2.1 91 8 1  1  3.1 86 5 0.2 4 5  2  1.1 81 9 0.5 0.5  9  3  2.5 60 4 15  3 3 6 10   5 4  4 5  65 20  10   5  2.4 75 5 4 5 6 5  7  4.1 80 3 5 2 10  0.3  6  3.2 65 5 4 6 5 4  6 5  8  5.1 96 4  9 10.8 90 5 5 10 10.0 80 2 6 2 5 1  4 11  1.8 80 5 15 12  2.6 84 11   5 13  3.3 80 2 10  2 6 15 12.0 90 7 0.3 3 16  5.4 69 2 20  2 1  3 3 12  6.0 91 4  5

TABLE 4 Dye Dye Content Water PG DEG NMP CET TBT TDG BDL PHO 2P P12  2 3.0 80 15 0.2   5  3 9.0 90 5 1.2  5  5 1.5 85 5 5 0.15 5.0 0.2  7 2.5 90 6 4 0.12  6 3.1 82 4 8 0.3  6  1 0.9 85 10  5 0.2   2 8.0 90 5 5 0.3  3 4.0 70 10  4 1  4 11   4 2.2 75 4 10  3 2  6 15 10.0  91 6  3 16 9.0 76 9 7 3.0 0.95  5 17 5.0 78 5 11   6 18 5.4 86 7  7  9 2.1 70 5 5 5 0.1  0.2 0.1 5 0.1   5 10 2.0 90 10  11 2   88 10   13 5   78 5 12    5 12 8   70 2 8 15    5 14 10   80 8   12 13 10   80 10 

What is claimed is:
 1. A mono-azo compound of Formula (1) or a salt thereof:

wherein: A is N, C—Cl, C—CN or C—NO₂; R¹ is H or optionally substituted alkyl; G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, —CF₃, halo or —PO₃H₂; L¹ and L² each independently is —SR², —OR³ or —NR⁴R⁵; R², R³, R⁴ and R⁵ each independently is H, optionally substituted alkyl or optionally substituted aryl; or R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted five or six membered ring; provided that L¹ and L² are free from carboxy, sulpho and —PO₃H₂ groups.
 2. A compound according to claim 1 wherein G is attached ortho to the azo group.
 3. A compound according to either claim 1 or claim 2 wherein G is sulpho.
 4. A compound according to any one of the preceding claims wherein A is N.
 5. A compound according to any one of the preceding claims wherein: R², R³, R⁴ and R⁵ each independently is H, C₁₋₃₀-alkyl optionally substituted by hydroxy, cyano, halo, nitro, C₁₋₆-alkoxy, C₁₋₆-hydroxyalkoxy, a 5 or 6 membered heterocyclic group or a group represented by T; or R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted morpholinyl, piperidinyl or piperazinyl ring; and T is an optionally substituted amino group.
 6. A compound according to claim 1 of the Formula (6) or a salt thereof:

wherein: X¹ and X² each independently is —O—, —S— or —NR¹²—; W¹ and W² each independently is H, a group T, —O(C₁₋₆-alkylene)OR¹⁰, C₁₋₆-alkoxy, hydroxy or a 5 or 6 membered heterocyclic group; R¹² is H or C₁₋₂₀-alkyl optionally substituted by hydroxy, C₁₋₄-alkoxy or a group T; R¹⁰ is H or alkyl optionally substituted by —NH₂; T is an optionally substituted amino group; p and q are each independently 1 to 20; or —X¹—(C_(p)H_(2p))W¹ and —X²—(C_(q)H_(2q))W² each independently form a piperazinyl, morpholinyl or piperidinyl ring; and R¹ is as defined in claim 1; provided that W¹, W² and R¹² are free from carboxy, sulpho and —PO₃H₂ groups.
 7. A compound according to claim 6 wherein: X¹ and X² each independently is —NR¹²—; and R¹² is as defined in claim 6; provided that W¹, W² and R¹² are free from carboxy, sulpho and —PO₃H₂ groups.
 8. A compound according to claim 6 wherein: W¹ and W² each independently is H, —OC₁₋₆-alkylene-OR¹⁰, C₁₋₆-alkoxy, —NH₂, —NR¹³CO(C₁₋₄-alkyl), hydroxy, morpholinyl or tetrahydrofuranyl; R¹³ is H or C₁₋₄-alkyl; and R¹⁰ is as defined in claim
 6. 9. A compound according to claim 1 of the Formula (7) or a salt thereof:

wherein: each Q independently is optionally substituted C₁₋₃₀-alkyl or a group of the Formula —Z—Q¹; each Z independently is a divalent linking group; each Q¹ independently is optionally substituted C₁₋₃₀-alkyl; m is 0 to 5; p is 1 to 20; and R¹ is H or optionally substituted alkyl; X¹ and X² each independently is —O—, —S— or —NR¹²—; and W¹ is H, a group T, —O(C₁₋₆-alkylene)OR¹⁰, C₁₋₆-alkoxy, hydroxy or a 5 or 6 membered heterocyclic group; wherein: R¹² is H or C₁₋₂₀-alkyl optionally substituted by hydroxy, C₁₋₄-alkoxy or a group T; R¹⁰ is H or alkyl optionally substituted by —NH₂; and T is an optionally substituted amino group; provided that W¹, X¹, X² and each Q are free from carboxy, sulpho and —PO₃H₂ groups.
 10. A compound according to claim 9 wherein: R¹ is H or C₁₋₄-alkyl; X¹ and X² each independently is —S— or —NR¹²—; R¹² is H, C₁₋₂₀-alkyl optionally substituted by hydroxy; W¹ is H, tetrahydrofuranyl or —OH; each Q independently is C₁₋₂₀-alkyl; and m is 0, 1 or
 2. 11. A compound according to either claim 9 or claim 10 wherein p is 5 to
 20. 12. A compound according to claim 1 wherein L¹ and/or L² contains an α-branched alkyl group.
 13. A compound according to claim 1 wherein: G is —SO₃H and is attached ortho to the azo group; L¹ and L² each independently is —NHR^(b); R^(b) is C₁₋₃₀-alkyl optionally substituted by one or more of furanyl, tetrahydrofuranyl, —OH or T; R¹ is H or C₁₋₄-alkyl; and T is an optionally substituted amino group.
 14. A compound according to any one of the preceding claims wherein the compound is in the form of an alkali metal, ammonium or substituted ammonium salt.
 15. An ink comprising: (a) from 0.01 to 30 parts of a compound of the Formula (9) or a salt thereof; and (b) from 70 to 99.99 parts of a medium comprising (i), (ii) or (iii): (i) a mixture of water and an organic solvent; (ii) an organic solvent free from water; or (iii) a low melting point solid; wherein all parts are by weight and the number of parts of (a)+(b)=100:

 wherein: L³ is L¹ or a labile atom or group; L⁴ is L² or a labile atom or group; A, R¹, G, L¹ and L² are as defined in claim 1; provided that L³ and L⁴ are free from carboxy, sulpho and —PO₃H₂ groups.
 16. A process for printing an image on a substrate comprising applying thereto an ink containing a compound of the Formula (9) or a salt thereof by means of an ink jet printer:

wherein: A is N, C—Cl, C—CN or C—NO₂; R¹ is H or optionally substituted alkyl; G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, —CF₃, halo or —PO₃H₂; L³ and L⁴ each independently is —SR², —OR³ or —NR⁴R⁵ or a labile atom or group; R², R³, R⁴ and R⁵ each independently is H, optionally substituted alkyl or optionally substituted aryl; or R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted five or six membered ring; provided that L³ and L⁴ are free from carboxy, sulpho and —PO₃H₂ groups.
 17. A process according to claim 16 wherein the ink comprises: (a) from 0.01 to 30 parts of a compound of the Formula (9) or a salt thereof; and (b) from 70 to 99.99 parts of a medium comprising (i), (ii) or (iii): (i) a mixture of water and an organic solvent; (ii) an organic solvent free from water; or (iii) a low melting point solid; wherein all parts are by weight and the number of parts of (a)+(b)=100:

 wherein: A is N, C—Cl, C—CN or C—NO₂; R¹ is H or optionally substituted alkyl; G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, —CF₃, halo or —PO₃H₂; L³ and L⁴ each independently is —SR², —OR³ or —NR⁴R⁵ or a labile atom or group; R², R³, R⁴ and R⁵ each independently is H, optionally substituted alkyl or optionally substituted aryl; or R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted five or six membered ring; provided that L³ and L⁴ are free from carboxy, sulpho and —PO₃H₂ groups.
 18. A paper, an overhead projector slide or a textile material printed by means of the process according to claim 16 or with an ink which comprises: (a) from 0.01 to 30 parts of a compound of the Formula (9) or a salt thereof; and (b) from 70 to 99.99 parts of a medium comprising (i), (ii) or (iii): (i) a mixture of water and an organic solvent; (ii) an organic solvent free from water; or (iii) a low melting point solid; wherein all parts are by weight and the number of parts of (a)+(b)=100:

 wherein: A is N, C—Cl, C—CN or C—NO₂; R¹ is H or optionally substituted alkyl; G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, —CF₃, halo or —PO₃H₂; L³ and L⁴ each independently is —SR², —OR³ or —NR⁴R⁵ or a labile atom or group; R², R³, R⁴ and R⁵ each independently is H, optionally substituted alkyl or optionally substituted aryl; or R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted five or six membered ring; provided that L³ and L⁴ are free from carboxy, sulpho and —PO₃H₂ groups.
 19. An ink jet printer cartridge containing an ink, wherein the ink contains a compound of the Formula (9) or a salt thereof

wherein: A is N, C—Cl, C—CN or C—NO₂; R¹ is H or optionally substituted alkyl; G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, —CF₃, halo or —PO₃H₂; L¹ and L² each independently is —SR², —OR³ or —NR⁴R⁵ or a labile atom or group; R², R³, R⁴ and R⁵ each independently is H, optionally substituted alkyl or optionally substituted aryl; or R⁴ and R⁵ together with the nitrogen to which they are attached form an optionally substituted five or six membered ring; provided that L³ and L⁴ are free from carboxy, sulpho and —PO₃H₂ groups. 